The OP wanted to know about airtags.
..from one of dozens of links..
an iPhone needs to be within a range of 33 feet to connect to any Bluetooth device,
according to Apple.
I'm very familiar with Bluetooth, as wella smost other RF techs since becoming an Avionics Tech in '74,even have some of the new <$1TI micros with it embedded inside.
The problem with using ANY Bluetooth device as a 'tracking device' is that it NEEDS to be nearby. Even under optimal conditions( ZERO obstructions, direct line of sight, perfect power,no EMI), BLE5 might get 300'(the best spec). This is all very well documented by the Bluetooth SIG. No BLE device will allow your cellphone to track your stolen tractor as it is hauled away. At best, the first 300' IF your cellphone is nearby.
Now Apple has a 'findit' feature that accesses millions of other Apple devices, to try to locate it. THAT is pretty dang scary, from a security aspect.